The Blueair Blue Signature Large (SP4i) in Nordic Fog is a cylindrical air purifier for living rooms and open-plan spaces, with a flat top that can also be used as a side table. The maker states that it cleans the air of 65 m² in 12.5 minutes and of up to 314 m² in one hour. Filtration runs in seven stages, combining electrostatic charging, a particle filter and a carbon layer with OdourFence technology for odours. The display adapts to the light in the room and shows air quality; the unit is run from its own controls or through the Blueair app over Wi-Fi, with four speeds, an automatic mode and a night mode. It works at 23 to 55 dB(A) and draws 3.5 to 42 W. It measures 44 x 40 x 40 cm, weighs 6 kg and ships with a washable Fog pre-filter and a particle and carbon filter.
When choosing an air purifier, compare the clean air delivery rate (CADR) with the size of the room, the type of filters and how much and how often they cost to replace, the noise level at the speed you will use at night and, if fitted, the air-quality sensor with an auto mode. Place it on the floor or on stable furniture with free space around the air inlets and outlets, and replace the filters as the manufacturer or the unit itself indicates.
The data shown comes from the documentation published by the manufacturer; in case of divergence the official datasheet prevails. The product is covered by the three-year legal guarantee of conformity (Spanish RDL 1/2007).
